1. E166 Collaboration J.C. Sheppard SLAC, October, 2003 E166 Background Test Simulations: Overview-what do we need J. C. Sheppard

2. J.C. Sheppard SLAC October, 2003 E166 Collaboration Meeting E-166 Background Tests Review and Advisory Committee Robert Noble (chair), C. Field, H. Lynch, and M. Ross ● Design a test in the FFTB to validate that the backgrounds in E-166 are acceptable ● Review results and recommend to Dorfan and Paterson to proceed with E-166 ● E-166 to be run in early calendar 2005 ● Background results roughly by end of calendar 2003

3. J.C. Sheppard SLAC October, 2003 E166 Collaboration Meeting E-166 Beamline Schematic 50 GeV, low emittance electron beam 2.4 mm period, K=0.17 helical undulator 0-10 MeV polarized photons 0.5 rad. len. converter target 51%-54% positron polarization

4. J.C. Sheppard SLAC October, 2003 E166 Collaboration Meeting E166 Polarimeter Overview 1 x 10 10 e -  4 x 10 9  4 x 10 9   4 x 10 7  4 x 10 9   2 x 10 7 e + 4 x 10 5 e +  1 x 10 3  2 x 10 7 e +  4 x 10 5 e +  Polarimeter  and Polarimeter

5. J.C. Sheppard SLAC October, 2003 E166 Collaboration Meeting E-166 Background Tests There are three sources of E-166 background: ● Streaming from up-beam of the undulator ● Interception at the undulator ● Secondaries produced in the spectrometer Background studies test the first two sources First meeting of R&A committee: June 26, 2003

6. J.C. Sheppard SLAC October, 2003 E166 Collaboration Meeting E-166 Background Test, June 2003 Shielding to be added as indicated by modeling

7. J.C. Sheppard SLAC October, 2003 E166 Collaboration Meeting E-166 Background Test, now

8. J.C. Sheppard SLAC October, 2003 E166 Collaboration Meeting E166 Background Test Goals The goals of the E166 Background Test are to transport a low emittance beam through a small aperture tube located at IP1 in the FFTB and to measure the background levels at the locations of the E166 detectors. Success for this test is demonstrated by being able to keep the beam on with the small aperture tube in place (loss levels below the FFTB radiation limits) and by measuring the background levels at each of 5 detectors to be less than 5% of the signal levels anticipated for E166 proper.

9. J.C. Sheppard SLAC October, 2003 E166 Collaboration Meeting E-166 Background Test For the background tests, a beam energy of 28 GeV is sufficient. A 1.2 mm id 1, 1 meter long, thin walled SS tube and a protection collimator will be installed at IP1. Five detectors: two Cerenkov- aerogel flux counters, a Si-W calorimeter, a Si-Pad calorimeter, and a CsI calorimeter will be located about 35 m downstream of IP1. Figure 1 shows the approximate layout of the required equipment in the FFTB enclosure. Shielding for the detectors, including Fe blocks representing the E166 magnetized absorbers, for the background tests is commensurate the full E166 experiment. Table 1 lists the expected E-166 signal strengths and 5% background levels

10. J.C. Sheppard SLAC October, 2003 E166 Collaboration Meeting E-166 Background Tests 1. The 0.9 mm aperture of the E-166 undulator is scaled inversely with the square root of the beam energy from the 50 GeV of E-166 proper to the 28 GeV of the background test. Thus.

11. J.C. Sheppard SLAC October, 2003 E166 Collaboration Meeting E166 Background Tests, Simulations Questions for the Simulations: ● How much lead ● How much Boron-Polyethylene ● How much blasts thru the 3 mm hole ● Do we need floor, ceiling, side wall shielding ● What is expected change from 28 GeV to 50 GeV We are concentrating on beam splat on the undulator tube and collimator, ignoring essentially everything else (upstream sources, synchrotron radiation, …). Are we fooling ourselves?